Automatic reclosing circuit breaker system



April 17, 1945. w. A. DERR 2,374,001

AUTOMATIC RECLOSING CIRCUIT BREAKER SYSTEM Filed 001;. 18, 1941 soa :3 "2 A? as, a. ll lees 3, 35 4 1% y;

are a ome a i n that i be So 11A La o) gr ds i ll F t me .iiW'S IQR E-Yflfil \C'LL3QENQ A. Wiihlinslmrg,

Westinghonse C5 Pennsylvania l8, lilo.

My invention relates, generally, to automatic reolosirg circuit breaker systems, and, more par ticularly, to a system for controlling the indi vidual ch cuit breakers or the separate poles oi a single circuit breaker, which control the sep arate conductors of a polyphase circuit.

"in the operation of polyphase power systems it has been found desirable to provide separate control for the separate conductors of the polyphase lhies so that, when a fault occurs on a single con= doctor, that conductor may be deenergized and reenergized without affecting the other conductors of the circuit to thereby maintain sumcient power on the circuit to keep the apparatus which is supplied by the system energized until the single conductor can be freed of its fault. However, it is not desirable to maintain power on less than all of the conductors of a polyphase circuit for any appreciable length of time, since a power circuit so operating causes considerable distiubance of neighboring communication cha'n nels, and is unable to prevent synchronous machinery from losing synchronism for a very long period of time.

It is an object of the invention, therefore, to provide a control system for the circuit breakers which control the conductors of a polyphase electric power circuit, which shall function to open any circuit breaker on whose associated conductor a. fault occurs, to reclose the opened circuit breaker, to open all of the breakers in the event that the originally opened breaker fails to remain closed when reclosed, to open all of the breakers in the event that any of the breakers stay open for more than a predetermined length of time, to indicate when any breaker is closed, to indicate when all breakers are open, and to indicate what breakers have been opened.

These and other objects and advantages of the invention will be apparent from the following detailed description, taken in connection with the accompanying drawing which is a diagrammatic view of an automatic reclosing circuit breaker system embodying the principal features of my invention.

In practicing the invention, circuit breakers 2, 4, and 6 are disposed to connect power supply conductors 8. l0 and I2 with load conductors l4, II and I8, respectively, of a three-phase power system. The breakers 2, 4 and 8 have trip coils 20, 22 and 24, respectively, and closing coils 24, 28 and 30, respectively. Protective relays 22, 24 and 38 are connected to energize the separate trip coils of the circuit breakers 2, 4 and 4, respectively, whenever a fault occurs on any of the function to prevent further reclosure of the cir-a cult breaker 2 unless a predetermined time has elapsed between any rclosure and the succeed ing opening of the breaker. The circuit breakers 4 and 6 have relays corresponding to the relays, 3Q, 40, 42, 44, 46 and 52, which function in a similar manner to control the circuit breakers 4 and 6, their associated signal lamps, and the common alarm 52. A pair of relays 54 and 88 functions in conJllnil-i tion with the relay 42 which is associated with the;

control system for the breaker 2, and corresponding relays associated with the breakers 4. and 6, function, in response to the second opening of any breaker within the time interval determined by the timing device 52, to open all of the break-. ers.

A timing relay 82 functions in response to the opening of any of the breakers 2, 4 and Bfor a predetermined length of time to open the other circuit breakers. Signal lamps B0 and B2 are controlled by the positions of the circuit breakers 2, 4 and i to indicate when all of the breakers are open and when any one or more of the breakers are closed, respectively. The alarm and the signal lamps 48 and the corresponding lamps associated with the breakers 4 and 8 may be de-. energized by a. reset switch 84. The breakers may be closed simultaneously when desired by the master control switch It.

Considering the invention in greater detail. the protective relays 32, 34 and 38 may be of any suitable type connected in any well known manner to respond to faults on the individual load conductors l4, l8 and It. When the protective relay 32 operates, it closes an energizing circuit for the tripping coil 20 of the circuit breaker 2 which extends from positive potential through the contact element 6'! of the relay 32, conductors I and 10, the winding of the tripping coil 20, a conductor 12, and a contact element 14 actuated by the circuit breaker 2 to negative potential. The energization of the tripping coil 20 will cause the circuit breaker 2 t open. The operation of the protective relay 32 also closes an energizing circuit for a. relay 38 which extends from positive potential through the contact element it of the relay 32, a conductor 78, a contact element 80 of the relay 42, a conductor 82, a contact element 8 of the relay 5t, conductors 86 and W2, a back contact element 87 of the relay 2%, conductors 96, 88, 89 and 90, the winding of the relay 38, a conductor 92, and a contact element 9% of the relay 9D to negative potential. The relay till is also momentarily energized by the actuation of the relay 32 since one terminal of its winding is connected to the conductor 96, and the other terminal is connected by conductor as and a contact element ltd which is actuated by the circuit breaker 2 to negative potential. The relay 4% is also energized by the actuation of the relay 32, one terminal of its winding being connected to the conductor m2, and the other terminal being connected to negative potential.

The momentary actuation of the relay to by the relay 82 until the circuit breaker opens to cause the contact element mil to break the energizing circuit of the relay (it will prevent the relay 88 from being fully actuated by moving the contact element at in the energizing circuit of the relay 38 to open circuit position until the circuit breaker 2 has opened to deenergize the relay Aid. When the relay 38 is fully actuated, its contact element ltd will close its own holding circuit extending from positive potential through the contact element ill l, conductors 83, 89 and all, the winding of the relay 38, the conductor 92 and the contact element 9 5 to negative potential. The actuation of the relay 3t will cause it to complete an energizing circuit for the closing winding 2% of the circuit breaker 2 which extends from'positive potential through a contact element ltd of the relay 38, a conductor lot, the closing winding 26 of the circuit breer 2, conductors H0 and H2, and a contact element i it of the relay fit to negative potential.

The relay? is a double winding relay having windings lit and lit which, when separately energized, move the contact element 80 to leftliand circuit-closing position and right-hand circuit-closing position, respectively, and the contact element at remains in the circuit closing position to which it is moved by the energize.- tion of one of the relay windings until moved into the other position by the energization of the other relay winding. When the relay 38 is actuated, its contact element lid closes an energizing circuit for the winding i it of the relay 32 which extends from positive potential through the winding lit, conductors H8 and I26, a contact element i2? of the relay 56 in back contact position, conductors lit and H2 and the contact element lid of the relay 38 to negative potential. The contact element at of the relay :32 will now be moved to the right-hand circuit-closing position to thus break the original energizing circuit for the relay 38 by the movement of the relay contact element as from its left-hand circuit-closing position, and preventing further energization of the relay 33 by the protective relay 32 until the contact element at of the relay a2 is again moved to the left-hand circuit-closing position.

When the circuit breaker 2 is closed by its closing coil 25, the time delay device 52 will be energized in a circuit which extends from a conductor X, which may be connected to one terminal of a suitable source of alternating current power, through the contact element 0 in the right-hand position, conductors H6 and 126, the winding of the timing device 52, a conductor asraooi i28, and a contact element I86 which is actuated by the circuit breaker 2 to a conductor Y which may be connected to the other terminal of the alternating current source of power.

The timing device 52 may be any suitable alternating current motor such as a single-phase synchronous motor or an induction disk-type motor having a rotor driven against the return bias of a spring element itl and driving a contact element me which engages stationary contact elements 833 after a predetermined interval of energization of the timing device 52. The contact element E32, after the time interval predetermined by the timing device 52, will close an energizing circuit for the winding N5 of the relay 62 which extends from positive potential through the winding lit, a conductor i364, the contact element I32 in engagement with the contact elements I38, a conductor use and a contact element ltd actuated by the circuit breaker 2 to negative potential. The energization oi. the relay winding H5 will move the contact element of the relay 62 from the right-hand circuitclosing position to deenergize the winding of the timing device 52 and permit the contact element l32 to be returned to its full-open position by the spring element Hi, and will move to the left-hand circuit-closing position to set up the energizing circuit for the relay 38 to be completed should any further actuation of the protective relay 32 occur.

When the relay 6% is actuated by the relay 32, its contact element N0 closes an energizing circuit for the relay at, extending from positive potential through the contact element bill, a conductor M2, the winding of the relay at, a conductor Md, and .a contact element of the release switch at to negative potential. The actuation of the relay 56 will cause its contact element M6 to close a holding circuit for the relay t8 extending from positive potential through the contact element hi6, conductors I68 and M32, the winding of the relay 66 a conductor SM, and the contact element of the release switch 65 to negative potential. The contact element E50 of the relay Qt will close an obvious energizing circuit for the signal lamp 33. A contact element its of the relay d6 will energize the alarm 50 in a circuit extending from positive potential through the contact element lad, conductors it and its and the alarm at to negative potential.

The relay dd is a slow to release relay so timed that the contact element ltd will not move to circuit-closing position upon the release of the relay dd until the circuit breaker has had sumcient time to close, o that the circuit controlled by the contact element itt will not be closed before the first reclosure of the circuit breaker 2. If, after the closure of the circuit breaker before the timing device 52 has closed its contact element I32 and while the contact element at is still in the right-hand circuit-closing position, the protective relay 8'2 should again be actuated, the circuit breaker 2 will be tripped as explained hereinbefore by the contact element 57 of the protective relay 32 and the contact element iSil which is actuated by the circuit breaker 2 will move to back contact position to close an energizing circuit for the relay 56 which extends from the conductor X through the contact element 56, the conductor i243, the winding of the relay 5%, a conductor la the contact element itt of the relay 35, a conductor 865, the contact element E36, a conductor its, a conductor itl, a contact element N3 of a relay 252 and a conductor M5 to the conductor Y. The actuation of the relay 84 will cause its contact element I88 to close energizing circuits for the windings of the relay 88 and relays I89 and I18 which are the relays associated with the circuit breakers 4 and 8, respectively, corresponding to the relay 88 which is associated with the circuit breaker 2. The energizing circuit for the relay 88 extends from the positiye potential through a contact element I1I actuated by the circuit breaker 4 in front contact position through conductors I12, I14, I18, I18, I88 and I82, the contact element I88 of the relay 84, conductors I84 and I88 and the winding of the relay 88 to negative potential. A similar energizing circuit is established for the relay I89 which has one terminal connected to the conductor I84 by conductors I88 and I98, and the other terminal connected to negative potential, and alike energizing circuit is established for the relay I18 which has one terminal connected to the conductor I84 by conductor I92 and the other terminal connected to negative potential.

The actuation of the relay I89 will cause its contact element I94 to close an energizing circuit for the tripping winding 22 of the circuit breaker 4, which extends from positive potential through the contact element I84 in front contact position, conductor I98 and I98, the tripping winding 22, a conductor 288 and a contact element 282 actuated by the circuit breaker 4 to negative potential. A similar energizing circuit for the tripping winding 24 of the circuit breaker 8 is closed by a contact element 284 of the relay I18 and extends from positive potential through the contact element 284 in front contact position, conductors 288 and 288, the tripping winding 24, a conductor 2l8 and a contact element 2I2 actuated by the circuit breaker 8 to negative potential.

The actuation of the relay I89 will also close an energizing circuit for a winding 2 of a relay 2 I 8 which corresponds to the winding I I8 and the relay 42, respectively. This energizing circuit extends from positive potential through the winding 2, a conductor 2I8, a contact element 228 of the relay I89 in front contact position, conductors 222 and 224 and a contact element 228 actuated by the circuit breaker '4 to negative potential. Thi circuit will be established only momentarily because of the movement of the circuit breaker 4 to open circuit position in response to the actuation of its tripping Winding 22. The contact element 228 of the relay 2I 8 corresponding to the contact element 88 of the relay 42 will thus be moved to the right-hand circuit-closing position. In a like manner, the energization of the relay I18 will cause the contact element 238 of the relay 23I which corresponds to the contact elements 228 and 88 of the relays 2l8 and 42, respectively, to move to the right-hand circuitclosing position.

While any of the circuit breaker 2, 4 and 8 is in closed circuit position, negative potential will be applied to the conductor 232, by the circuit breaker 2 through a contact element 234, by the circuit breaker 4 through a contact element 238 and the conductor 238, and by the circuit breaker 8 through a contact element 248 and a conductor 242, and this negative potential and will be applied to one terminal of each of the lamps 88 and 82 through conductors 244 and 248. Since negative potential is applied to the other terminal of the lamp 80, the lamp 88 will not be energized, and since positive potential is applied to the other terminal of the lamp 82, the lamp 82 will be energized while any one of the circuit breakers 2, 4

and 8 is in closed circuit position. When all oi the circuit breakers 2, 4 and 8 are in open circuit position, positive potential will be applied to the terminals of the lamp 88 and 82 which are interconnected by the conductor 248 in a circuit which extends from positive potential through the contact element 234 in back contact position, a conductor 248, the contact element 238 in back contact position, a conductor 288, the contact element 248 in back contact position, and the conductors 232, 244, and 248. The lamp 88 will thus be energized and the lamp 82 deenergized.

When .the circuit breakers are open and it is desired to close them, the manual control switch 88 may be actuated to close an energizing circuit for a relay 282 which extends from positive potential through the contact element of the control switch 88, a conductor 254, and the winding of the relay 252 to negative potential. A contact element 258 of the relay 252 will close an energizing circuit for the relay 38 which extends from positive potential through the contact element 258, conductors 89 and 98, the winding of the relay 38, the conductor 92, the contact element 84 of the relay 48 to negative potential. A similar energizing circuit is established for the relay 283 by a contact element 285 of the relay 252 for closing the circuit breaker 4 and extends. from positive potential through the contact element 285, conductors 288 and 282 to winding of a relay 283 which corresponds to the relay 38 associated with the circuit breaker 2, a conductor 284 and a contact element 288 which corresponds to the contact element 94 of the relay 48 to negative potential. Likewise, a contact 281 of the relay 252 causes the closure of the circuit 8 by completing an energizing circuit for relay 218 extending from positive potential through the contact element 281, a conductor 258, a conductor 288, the winding of a relay 210 associated with the circuit breaker 8 in the same manner that the relay 38 is associated with the circuit breaker 2, a conductor 212 and a contact element 214 which corresponds to the contact elements 94 and 288 to negative potential.

Should any of the circuit breakers 2, 4 and 8 be tripped for any reason other than the actuation of their associated protective relays 32, 34 and 38, such as failure to properly latch when reclosed, the tripped breaker will cause the actuation of the common time delay relay 58. Should the circuit breaker 2 open, for instance, its contact element 218 will close an energizing circuit for the relay 58 which extends from positive potential through the contact element I1I actuated by the circuit breaker 4, conductors I14, I18 and I18, the contact element 218, a conductor 218 and the winding of the relay 58 to negative potential. Should the circuit breaker 4 be opened. its contact element "I will close an energizing circuit for the relay 58 which extends from positive potential through a contact element 288 which is actuated by the circuit breaker 8, conductors 282, 284, I18 and I18, the contact element "I in back contact position, conductors 288, 288 and 218 and the winding of the relay 58 to negative potential. A similar energizing circuit will be closed by the contact element 288 of the circuit breaker 6 in back contact position if the circuit breaker 8 be open. After a predetermined period of energization, the relay 58 will close its contact element 298 to apply a positive potential to the conductor I84 in a circuit which extends from positive potential through the contact element 298 and a conductor 292 to the conductor I8 5. The relay 58 will thus be energized since it has one terminal connected to the conductor I86 and the other connected to the negative potential. Similarly, the relay 169 associated with circuit breaker Q will be energized since it has one terminal connected to negative potential and the other terminal connectedto the conductor ltd through the conductors W8 and Nd and the relay H associated with circuit breakerfi will be energized since it has one terminal connected to negative potential and the other connected to the conductor it through the conductor 682. The energization of the relays 56, I69 and no will complete tripping circuits for the circuit breakers 2, d and 6, respectively, as explained in detail hereinbefore, Thus when any circuit breaker stays open for the interval of time predetermined by the time delay of closing of the relay 58, which interval is longer than the normal period required by the first reclosure of any circuit breaker when it is opened by its associated protective relay, all of the circuit breakers will be opened to prevent the load circuit from being energized for any appreciable period of time by single-phase potential.

When it is desired to trip the circuit breakers 2, s and t, a manual control switch 295 may be actuated to connect positive potential to the conductor H85 in a circuit which extends from positive potential through the control switch 2% and a conductor 2% to the conductor I86. The application of positive potential to the conductor use will energize the relays as, IE9 and are which, in turn, will trip all of the circuit breakers as fully explained hereinbefore. When any circuit breaker has been tripped and the alarm 5d and the signal associated with the individual breaker have been energized, the signals may be reset by actuating the reset switch 6% to open the holding circuit of the signal relay 66 which is associated with-the circuit breaker 2 and the corresponding signal relays associated with the circuit breakers t and 5.

In the operation of the system, when a fault such as a ground fault occurs on any of the conductors as, It, and it, its associated protective relay 82, 3% or 38 will cause the circuit breaker on the circuit on which the fault occurs to open and reclose immediately. If the reclosed circuit breaker remains closed, the timing device associated with the breaker such as the timing device 52 associated with the breakerfi will be energized, and after its timing interval, will reset the reclosing circuit so that the breaker will again be immediately reclosed if tripped by a fault. However, if the circuit bre'aker is again tripped by a fault before the time interval of the timing device has elapsed, the other circuit breakers will also be tripped and all of the circuit breakers will be locked in open circuit position until reclosed by the manual control switch-6B. When a circuit breaker opens, a common alarm 5t will be sounded and a signal lamp will be illuminated to indicate which of the breakers has opened, and this alarm and signal lamp indication will be retained until the reset button 66 is manually actuated. In order that the operator may have a positive indication of the position of the breakers, a signal lamp 550 is provided and is illuminated only when all of the breakers are in open circuit position, and a signal lamp 62 is illuminated when any of the breakers is in closed circuit position.

It is to be understood that while the invention aevaooi h been shown and described as controlling a three-phase circuit, it is equally as well applicable to other polyphase circuits such as twophase or six-phase circuit wherein a part of the circuits may be isolated for a short interval to clear faults which may occur upon the circuits but where it is not desired to operate the load circuit for any appreciable interval of time with less than the full number ofload conductors energized.

Thus, it will be seen that I have provided a control system for-the circuit breakers which control the conductors of a polyphase elecn'ic power circuit which shall function to open any circuit breaker on whose associated conductor a fault occurs, to reclose the opened circuit breaker, to open all of the breakers in th event that the originally open breaker fails to remain closed when reclosed. to open all the breakers in the event that any of the breakers stay open for more than a predetermined length of time, to indicate when any breaker is closed, to indicate when all breakers are open, and to indicate when breakers have been opened.-

In compliance with the requirements of the patent statutes, I have shown and described herein a preferred embodiment of my invention. It is to be understood, however, that the invention is not limited to the precise construction shown and described herein, but is capable of modification by one skilled in the art, the embodiment herein shown being merely illustrative of the principles of my invention.

I claim as my invention:

1. In a control system for a plurality of circuit breakers which control the separate phase conductors of a polyphase circuit, means including a fault responsive relay responsive to faults on the individual phase conductors of th circuit for automatically opening the circuit breaker which controls the conductor on which the fault occurs, means controlled by said fault responsive relay for automatically reclosing any such opened breaker, means for opening each of the other breakers automatically in the event that the originally opened breaker is again opened when reclosed within a predetermined time interval, a timing relay common to all the breakers, means whereby said timing relay causes all of said circuit breakers to open after a predetermined period of time of greater duration than the aforesaid predetermined time interval, and means responsive to the position of any one of the circuit breakers for continuously energizing said timing relay so long as any one of the circuit breakers is open.

2. In a control system for a plurality of circuit breakers which control the separate phase conductors of a polyphase circuit, opening means for each of said circuit breakers, closing means for each of said circuit breakers, a control system for each of said circuit breakers comprising fault responsive means responsive to faults on the individual conductor which is controlled by the circuit breaker, means responsive to the operation of the fault responsive means for actuating only the associated circuit breaker opening means, control relay means responsive to the operation of the fault responsive means and the opening of the circuit breaker for actuating the circuit breaker closing means to effect a reclosure of the breaker, relay means responsive to the operation of the circuit breaker closing means for rendering the breaker closing means inoperative to respond to said fault responsive means, a timing device, means responsive to the operation of the said control relay mean for initiating the operation of said timing device, means responsive to the timing device after a predetermined time interval of operation of the timing device for rendering said control relay means again operative to respond to the fault responsive means, and means individual to each breaker responsive to their opening of the circuit breaker during the said predetermined time interval for immediately actuating the opening means ofeach of the other breakers.

3. In a control system for a plurality of circuit breakers which control the separate phase conductors of a polyphase circuit, opening means for each of said circuit breakers, closing means for each of said circuit breakers, a control system for each of said circuit breakers comprising fault responsive relay means responsive to faults on the individual conductor which is controlled by the circuit breaker, means responsive to the operation of any one of the fault responsive means for actuating its associated circuit breaker opening means, means responsive to the operation of the fault responsive means and the opening of the circuit breaker for actuating the circuit breaker closing means, means responsive to the operation of the circuit breaker closing means'for rendering the breaker closing means inoperative to respond to said fault responsive means, a timing device associated with each of the breakers, means responsive to the operation of the breaker closing means and the closure of the breaker for actuating its associated timing device, means responsive to the timing device after a predetermined time interval of operation of the timing device for rendering said breaker closing means'operative to again respond to the fault responsive means, means responsive to the reopening of the circuit breaker during the said predetermined time interval for actuating the opening mean of each of the other breakers, an additional timing de- -vice common to all breakers, means responsive to the opening of any one of the circuit breakers for actuating said second timing device, and means responsive to the actuation of said second timing device for a predetermined interval of time of greater duration than the aforesaid predetermined time interval for opening the remainder of the circuit breakers.

4. In a control system for a plurality of circuit breakers which control the separate conductors of a plural conductor circuit, means including fault responsive relay means individual to each conductor responsive to predetermined conditions on any of the separate conductors for opening only the circuit breaker on whose associated conductor the predetermined condition occurs, means controlled by said fault responsive means for automatically reclosing any such opened breaker and for rendering the fault responsive relay means ineffective to effect a subsequent reclosure of the breaker unless it remains closed for a predetermined time interval, and means including a time delay relay associated with each breaker for opening a plurality of the breakers automatically in the event that any such originally opened and reclosed breaker is again opened within a different predetermined time interval of lesser duration than the aforesaid predetermined time interval after the reclosure thereof.

5. In a control system for a plurality of circuit breakers which control the separate conductors of a plural conductor circuit, means includ= ing fault responsive relay means individual to each conductor responsive to predetermined conditions on any of the separate conductors for opening any of the circuit breakers on whose associated conductor the predetermined conditions exist, means controlled by said fault responsive relay means for automatically reclosing any such opened breaker immediately upon the opening thereof, means individual to each breaker for opening all of the other breakers automatically in the event that the originally opened and reclosed breaker is again opened within a predetermined time interval, and means including time delay relay means common to all the breakers and controlled by electrically interlocked contact members on all the breakers for automatically opening all of the breakers in the event that any one of the breakers is opened for any reason other than in response to said predetermined conditions by said fault responsive means.

6. Means for controlling the respective opening-means and closing-means of a plurality of single-pole circuit-interrupters in the separate phase-conductors of a polyphase line, comprising the combination with said circuit-interrupters, of three protective relaying-means for effecting three predetermined relaying-operations, one for each of the three phase-conductors of said line, circuit-means for energizing the opening-means and the closing-means of only one of the three circuit-interrupters in response to a relaying-operation of its associated protective relaying-means to effect the opening and an immediate reclosure of the breaker, and means including timing relay means individual to each breaker jointly responsive to the initial operation of the protective relaying-means and the reclosure of the interrupter for limiting the number of successive reclosing operations in response to successive operations of the protective relaying-means which will be permitted for any one of said circuit-interrupters to a predetermined number within a predetermined time interval. and time delay relay means individual to each interrupter and initiated into operation by the first operation of the protective relaying means for effecting the energization of the opening means of the other interrupters in the event that the interrupter which has been opened and reclosed does not remain reclosed within said predetermined interval as determined by its individual timing relay means.

7. Means for controlling the respective opening-means and closing-means of three singlepole circuit-interrupters in the three phase-conductors of a three-phase line, comprising the combination with said circuit-interrupters, of three protective relaying-means for effecting three predetermined relaying-operations, one for each of the three phase-conductors of said line, circuit-means for energizing the opening-means and the closing-means of only one of the three circuit-interrupters in response to a relayingoperation of its associated protective relayingmeans to open and reclose the interrupter, additional circuit-means individual to each interrupter for energizing only the opening-means thereof, a control relay individual to each interrupter operable to energize said additional circuit means of all three interrupters, and a time delay relay individual to each interrupter operable to eifect the operation of its associated control relay in the event that the reclosed interiI-fa' rupter reopens within a predeieed time in terval after the recloeurethereof.

8. In a control system for a plurality of air cuit breakers which control the separate e0nductors of a plural conductor circuit, fault responsive relaying means individual to each breaker and responsive to the faulted conditions oi-thie separate conductors for causing an opening operation of only the breaker mociated with the faulted conductor, control relay means conditioned, for operation by the operation of the fault responsive relaying to open breaker and finally responsive to the o asraeer the breaker for automatically reclosing the opened breaker, means controlled by said we troi relay means for rendering the fault r sive relaying means inefiective to again initiate areclosure of the breaker unless it w. i

- closed for a predetermined time interval afte its initial reclosure, and relay means individual to each breaker for effecting opening operations of the remaining breakers upon the opening of the breaker associated with the faulted conductor in the advent that said breaker reopens within said predetermined time interval 

